Advance Journal of Food Science and Technology 10(7): 483-486, 2016
DOI: 10.19026/ajfst.10.2169
ISSN: 2042-4868; e-ISSN: 2042-4876
© 2016 Maxwell Scientific Publication Corp.
Submitted: March 14, 2015
Accepted: March 24, 2015
Published: March 05, 2016
Research Article
Preliminary Study on the Quality of Pasteurized Milk in Two Factories in Sudan
1
Nawal Noureldaim Abuelhassan, 1Sahilah Abdul Mutalib, 3Mohammed Tajeldin Ibrahim, 2El Mubarak
Musa Tibin, 2Najeeb Kaid Nasser Al-Shorgani, 2Febri Doni and 2Wan Mohtar Wan Yusoff
1
School of Chemical Sciences and Food Technology,
2
School of Biosciences and Biotechnology, Faculty of Science and Technology, Universiti Kebangsaan
Malaysia, 43600 UKM Bangi, Selangor, Malaysia
3
College of Veterinary Medicine and Animal Production, Sudan University of Science and Technology,
P.O. Box 204, Hillat Kuku, Khartoum, Sudan
Abstract: A total of thirty (n = 30) packaged pasteurized milk samples were collected from two factories in
Khartoum (A) and White Nile (B) States, Sudan and investigated to determine their physical, chemical properties
and bacterial quality. The results revealed that no significant differences in color, taste, flavor and consistency of the
samples. Clot on boiling test revealed that no acidity on day 3 and 6 post production. However, on day 9, 40% (for 6
samples) from factory A and 20% (for 3 samples) from factory B were positive due to ineffective pasteurization.
Titratable acidity test met the standards of Sudanese Standard and Metrology Organization (SSMO) in acidity
degree for both factories (p>0.05). Phosphatase test revealed that only 6.7% of samples from factory A were
positive. Total number of nonpathogenic bacteria test showed high significant differences (p<0.01). The presence of
Escherichia coli at the rate of 6.7% in factory A and 60% in factory B indicates fecal contamination which
demonstrated the hygiene procedures in milk preparation for both factories which should be taken consideration
before it was contributed to consumers.
Keywords: Milk pasteurization, milk quality control, Sudan
sp. Nevertheless, other food pathogen which is also
may survive one such as Salmonella sp., Escherichia
coli, (Salo and Wirtanen, 2005).
In Sudan, pasteurization of milk is covered by
multiple private firms including Khartoum State and
White
Nile.
However,
contamination
of
microorganisms during milk processing could lead to
the reduction of milk quality (Harding, 1999). Milk
contamination is major constraint to milk industry in
Sudan due to low quality milk supplies for consumers
(Mohamed and Ibtisam, 2007). High quality standard of
milk is possible by monitoring the quality of end milk
products prior before distribution (Smit, 2005). In this
study, the quality of pasteurized milk produced by two
factories in Khartoum and White Nile States were
examined for preliminary test of chemical, physical and
bacteriological aspects as in accordance to Sudanese
Standards and Metrology Organization (SSMO).
INTRODUCTION
Sudan is one of the biggest countries in area of
1,886,068 km2 of territory. The grazing lands compose
40.4% from total Sudan area. The pastoralists of Sudan
own 90% of the nation herds of livestock according to
the Ministry of Animal Resource and Fisheries (MARF,
2008). Among the Arab countries, Sudan ranks first and
second in Africa with respect to animal production.
Recently, the livestock estimation found that there are
about 50 million heads of sheep, 40 million heads of
cattle, 43 million heads of goat and 4 million heads of
camel (MARF, 2008). The consumption of milk in
Sudan per capita was estimated in 1999, at 219.7
kg/annum (Ahmed, 2006). It is believed that production
of milk increasing in the future.
Milk is good medium for several bacteria to
develop and grow. Pasteurized is one of the most
famous methods to eliminate and control the bacterial
growth (Heeschen, 1994). However, pasteurization may
not destroy all microflora due to inadequate or faulty
during milk processing production. It also can survive
as the medium for heat resistant bacteria which most
frequencies involves Bacillus cereus and Clostridium
MATERIALS AND METHODS
Samples collection and preparation: A total of thirty
pasteurized milk samples (n = 30) were purchased from
Corresponding Author: Nawal Noureldaim Abuelhassan, School of Chemical Sciences and Food Technology, Faculty of
Science and Technology, Universiti Kebangsaan Malaysia, 43600 UKM Bangi, Selangor, Malaysia
This work is licensed under a Creative Commons Attribution 4.0 International License (URL: http://creativecommons.org/licenses/by/4.0/).
483
Adv. J. Food Sci. Technol., 10(7): 483-486, 2016
groceries in Khartoum (15) and White Nile States (15).
The pasteurized milk from Khartoum was packed in
cartoon. While from White Nile state was packed in
plastic container. Both products were stored at
refrigerator (4°C) and had validity period of 7 days. All
samples were collected during the period from March to
April, 2007. The samples were immediately kept into
refrigerator (4°C) until used.
Clots On boiling (CO): The coagulation tests were
performed as described by LPC (1999). A total of 5 mL
of milk was boiled in a test tube and if coagulation was
shown the milk contain high acid.
Acidity test: Acidity test was conducted according to
Richardson (1985). Nine ml of milk was placed into the
conical flask, five drops phenolphthalein were added
and titrated with 0.1 N NaOH until faint pink color
appeared. The volume of sodium hydroxide solution
was then divided by 10 and expressed as percent of
lactic acid production.
Physical tests: Sensory evaluation was performed as
described by Campbell and Marshall (1975). Sensory
was done to evaluate odor, sight, color and taste. Milk
panels were chosen from milk handler, milk
management and students who are experienced in milk
evaluation.
Statistical analysis: ANOVA and t-test (Gomez and
Gomez, 1984) at significance level of p<0.05 and the
Statistical Package for Social Sciences (SPSS) program
were used.
Phosphatase enzyme test: The phosphatase analysis in
milk was evaluated using Lactognost rapid phosphatase
test (Heyl, Berlin). The test was done according to the
Manufacture's instruction. Five milliliter of milk was
poured into 2 test tubes namely, A (sample of
pasteurized milk) and B (raw fresh milk as control).
One tablet of Lactognost I, a tablet of Lactognost II and
spoon full of Lactognost III were added into the labeled
test tubes (A and B). Both tubes were incubated at 37°C
for 20 min. After incubation, if the blue color appeared
it indicates positive result for phosphatase activity.
While brown color indicates negative result (no
phosphatase activity).
RESULTS AND DISCUSSION
A total of thirty packaged pasteurized milk samples
from factory A and B were collected randomly from
different sources during this study to investigate the
color, taste, flavor and consistency evaluation, degree
of acidity, adequate efficiency pasteurization and
bacterial quality. The results also showed that no
significant difference between the pasteurized milk of
the two factories. Panel test revealed acceptable to less
acceptable taste. Similarly, the consistency was neither
affected by the source nor by the storage period.
Nonetheless, it varied from watery to thick.
The pasteurized milk of both factories (A and B)
showed similar white-creamy color. No significant
change in color or in taste was observed due to storage
on days 3, 6 and 9, respectively as shown in (Table 1).
In phosphatase test, it showed that all samples
tested in factory B were free of phosphatase as
indicated by brown color. While, 6.7% of the samples
obtained from factory A revealed blue color, indicating
the presence of phosphatase. This indicated that the
pasteurized milk of factory A did not meet the
standards of SSMO (2007), while factory B followed
with food standard which given by SSMO (2007). Smit
(2005) and Richardson (1985) reported that a negative
result for phosphatase test showed the proper
pasteurization processed was applied on the milk
product (Table 2).
Total Bacterial Count (TBC): The Total Bacterial
Count (TBC) was carried out according to Andrewes
(1997). Milk samples was diluted from 10-1 to 10-4 and
spread onto Plate count agar medium in duplicate (5
g/L casein enzymatichydrolysate, 2.5 g/L yeast extract,
1 g/L dextrose and 9 g/L agar; CDH, USA). The
plates were incubated at 37°C for 24 h. The colonies
were counted and recorded as an according to
ISO (1991).
Isolation of Escherichia coli: Sample was streaked
onto Eosin Methylene Blue (EMB) (Oxoid) plate
medium and incubated at 37°C for 18-24 h.
Visualization was performed for E. coli colonies on
EMB plate by metallic sheen.
Table 1: The sensory evaluation (color, taste, consistency and flavor) of the two factories at day 3, 6 and 9, respectively post pasteurization
Color
Taste
---------------------------------------------------------------------------------- --------------------------------------------------------------------3 day
6 day
9 day
3 day
6 day
9 day
Factory
*A
2.68±0.48
2.92±0.57
2.80±0.41
3.1±0.60
3.50±0.50
2.75±0.50
*B
2.84±0.62
2.64±0.48
2.70±0.47
3.5±0.57
3.21±0.44
3.00±0.84
Consistency
Flavor
---------------------------------------------------------------------------------- --------------------------------------------------------------------Factory
3 day
6 day
9 day
3 day
6 day
9 day
2.92±0.29
*A
3.12±0.44
3.28±0.61
3.13±0.52
3.00±0.00
2.8±0.45
*B
3.20±0.71
3.28±0.61
3.35±0.67
3.00±0.82
3.7±0.50
3.31±0.75
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Adv. J. Food Sci. Technol., 10(7): 483-486, 2016
Table 2: Phosphate test in two milk factories in Sudan
Phosphate test (%)
----------------------------------------------ve
+ve
Factory
A
93.3
6.7
B
100
0.0
-ve: Negative; +v: Positive; 15 samples for each factories (A and
B)
pasteurized milk, 6.7% of the milk samples of factory A
gave positive result for E. coli, while those of factory B
gave 60% (Table 4). This can be attributed to poor
hygienic production or ineffective pasteurization of
milk (Harding, 1999). This result agreed with Dasilva
et al. (2001) who isolated E. coli from pasteurized milk
and this represents a potential risk for children. Also
agree with Sayed (2006) but disagree with the health
condition of SSMO (2007). In developing countries
there is no doubt that the Entero Toxigenic E. coli
(ETEC) are important organism responsible for causing
of diarrhea in all age groups in areas of poor hygiene,
particularly in tropics where isolation rate of ETEC
ranged between 10 and 70%. These records are
collected from children and adults suffering from
diarrhea (Gross and Row, 1985).
The presence of E. coli indicates faecal
contamination and specifically in enteric pathogen. The
high percentage of E. coli 60% obtained in this study
might be due to improper handling, poor cleaning of
equipments as stated by Hayes et al. (2001) (Table 4).
Concerning the clot on boiling test the samples of
the pasteurized milk of factory A and B were negative
at the third and six days after production and this is in
accordance with standards given by SSMO (2007). On
day 9, 40 and 20%, of milk samples of factory A and B
clotted, respectively. It is well-known that the shelf life
of pasteurized milk is 7 days as reported by SSMO
(2007).
The clot on boiling test was negative to all samples
collected from both factories on day 3 and 6 post
pasteurization. Results also showed that no significance
in all samples of both factories. However, 40 and 20%
of samples were significant on day 9 post pasteurization
in factory A and B, respectively.
The titratable acidity showed no significant
differences on day 3 and 6 for both factories in the
obtained values compared to the SSMO. However, it
was significantly (p<0.05) higher than that of the
SSMO on day 9.
The results obtained for acidity degree showed no
significant difference between the milk of the two
The total bacterial counts results of the current
study (Table 3) showed a significant effect of storage
time (3, 6 and 9 days, respectively) on total bacterial
counts. It can also be seen that the pasteurized milk of
factory B contain higher total bacterial count than that
of factory A.
The results obtained for the total bacteria counts
represent high significance (p<0.05) at level of
concentration (104) between the milk produced by the
two factories A and B (Table 2). The results disagrees
with the health condition of pasteurized milk for the
total bacteria counts (nonpathogenic organisms shall be
less than 50,000 cells/mL) as given by SSMO (2007).
The high bacterial counts were expected under tropical
conditions like in Sudan due to the fact that high
temperature enhances growth and multiplication of
bacteria.
Under tropical condition many factors such as high
temperature, absence of sanitary condition for
production of milk in the dairy farms and unavailability
of cooling during handling and transportation of milk
affect the quality of milk. Also, absence of application
of principles of Hazard Analysis Critical Control Point
(HACCP) system, which includes all concepts of
sanitary regulation and hygienic practices contribute a
lot to the production of Unhealthy pasteurized milk as
stated by Harrigan and Park (1991).
E. coli was isolated from the samples using EMB
medium as mentioned in materials and methods. The
colonies of E. coli appeared as green metallic color on
EMB medium. Test of E. coli showed higher values
(60%) from factory B were positive to E. coli compared
to (6.7%) from factory A. Presence of E. coli in high
values as the results showed indicating high
contamination. Concerning the presence of E. coli in
Table 3: Total bacterial count (104) and titratable acidity test of the pasteurized milk of factories: A and B at day 3, 6 and 9, respectively post
pasteurization
Total bacterial count (104)
Titratable acidity
-------------------------------------------------------------------------------------- ------------------------------------------------------------------Factory
3 day
6 day
9 day
3 day
6 day
9 day
*A
1040.6±1617.6
349.9±495.6
10.0±14.10
0.21±0.02
0.21±0.02
0.27±0.09
*B
161.1±197.4
963.4±1703.0
1009.9±1685.62
0.21±0.02
0.21±0.02
0.23±0.02
Table 4: E. coli test in two milk factories in Sudan
Factory
A
B
-ve: Negative; +v: Positive; 15 samples for each factories (A and B)
E. coli (%)
-----------------------------------------------------------------------------------------ve
+ve
93.3
6.7
40
60
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Adv. J. Food Sci. Technol., 10(7): 483-486, 2016
factories A and B and this comes in agreement with
SSMO which gives a rate of 0.18 lactic acid %.
Previously, it was reported that that the mean of
titratable acidity for Sudanese cattle milk was in the
range of 0.16-0.22 with a mean of 0.19 lactic acid %
which is agree with our study (Idris et al., 1975).
Harding, F., 1999. Milk Quality. 1st Edn., Chapman
and Hall Food Science Book, Aspen Publishers,
Inc., Gaitherburg, Mary Land, pp: 102-104.
Harrigan, W.F. and R. Park, 1991. The hazard analysis
critical
control
point
system
and
its
implementation. In: Making Safe Food: A
Management Guide for Microbiological Quality,
pp: 146-148.
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and K.J. Boor, 2001. Identification and
characterization of elevated microbial counts in
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(Eds.), Euterund Gesäugekrankheiten. Gustav
Fischer Verlag, Jena, Stuttgart, Germany, pp: 138180 cited in Eberlein (2007).
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CONCLUSION
From the present study it can be concluded that; the
general and health conditions for the production of
pasteurized milk given by Sudanese Standards and
Metrology Organization are applied partially by some
factories. Low quality pasteurized milk were distributed
in Khartoum in terms of high total counts of bacteria
and presence of E. coli.
ACKNOWLEDGMENT
The authors wish to acknowledge financial support
provided from the Malaysian Technical Cooperation
Program (MTCP).
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